1. Field of the Invention
The invention relates to a portable hoist, and more particularly relates to a portable hoist adapted to remove a load from a vehicle, transport the load to a site and in combination with a ladder, lift the load to a rooftop and transport the load to an installation position.
2. Description of the Prior Art
In the past, various portable hoists and load carrying devices have been used to transport objects across level surfaces and in combination with a ladder for hoisting objects to elevated locations such as rooftops or the like. An example of a load carrying device would be a gantry supported by wheeled dollies which transports an object across level ground. An example of a hoisting device used in combination with a ladder would be a substantially rectangular framework having rollers thereon which fit along the side rails of a ladder to allow hoisting and rolling of the framework and an attached load up the ladder to the level of a roof top thereby placing the entire load on the ladder members. These and other known hoist devices are useful but none provide a means of unloading an object from a vehicle such as a truck, transporting the object to the ladder and then hoisting the object up to the top of the building and placing it in position on a flat or slightly inclined rooftop without subjecting the ladder to undue stresses.
U.S. Pat. No. 3,093,209, issued to L. Nagy, discloses a combination step ladder/scaffold which teaches the use of a step ladder element, prop element and platform element which pivot with respect to each other to collapse the apparatus. The device further teaches the ladder element having wheels for its own transportation.
U.S. Pat. No. 3,722,621, issued to M. L. Jones discloses a ladder bench having horizontal telescopic bench surface mounted on ladder suporting elements located at each end. The ladder support elements are extendable so that the bench may be raised to a scaffold height. The supports are hingedly attached to the bench element so that the apparatus may be collapsed for storage or transportation.
U.S. Pat. No. 3,494,492, issued to W. E. Thiermann discloses a horizontal beam member supported by two posts capable of being extended, both posts being supported by wheels. A load support and hoist member is disclosed but does not provide for collapsibility of the device nor adaptation to a ladder.
U.S. Pat. No. 2,606,001, issued to C. E. Lepper, discloses a wheeled structure arranged to lift and transport heavy articles by means of a cable and hook provided on a horizontal member.
U.S. Pat. No. 2,573,604, issued to J. C. Richardson, et al., discloses a horizontal wheeled U-shaped frame with a hoisting element mounted on a cross-beam.
U.S. Pat. No. 2,798,574, issued to R. D. Wardell, discloses a scaffold with a hoist structure mounted thereon having a pulley cable and a hoist cage which can be raised and lowered to the level of the scaffold.
U.S. Pat. No. 2,706,057, issued to H. F. Belding, discloses a structure providing a hoist element comprised of a cable, reels and pulley mounted on one of the legs provided.
U.S. Pat. No. 4,183,423, issued to J. P. Lewis, and U.S. Pat. No. 2,405,505, issued to A. J. Kleidon, both disclose a ladder hoist in which the hoisting mechanism is provided integral with the ladder. The Lewis patent discloses a cable on a winch which runs over a pulley on the top section of the ladder and is connected to a carriage having wheels running in channel-like sides of the ladder member.
U.S. Pat. No. 3,666,054, issued to F. L. Ellings, et al., discloses a hand truck mounted on rollers arranged for engagement with the rails of a ladder and a winch for movement of the hand truck up and down the ladder.
U.S. Pat. No. 2,599,169, issued to F. B. Finney, discloses a bracket for supporting the top of a ladder away from a wall, the bracket being attachable and detachable from the ladder without the use of tools. However, this device places high stresses on the ladder members because it does not properly support the rooftop end and, therefore, has limited capacity. It further does not teach hinging of the ladder while supporting the rooftop end to prevent undue stresses in the ladder.
None of the previous art solves the need for an apparatus which can be operated by one man and is capable of removing a load from a vehicle, transporting the load to a ladder, hoisting the load up to a roof top, placing the load on the roof top and transporting the load across the roof top to a desired installation position.